Murine models of Pneumocystis infection recapitulate human primary immune disorders

Area of Science:

• Immunology
• Infectious Diseases
• Genetics

Background:

• Pneumocystis pneumonia (PCP) is an AIDS-defining illness, with risk inversely correlated to CD4+ T cell counts.
• Current PCP epidemiology is driven by primary immunodeficiencies and immunosuppression, not solely HIV.
• The utility of murine models for human diseases, particularly immunodeficiencies, is under continuous evaluation.

Purpose of the Study:

• To assess the validity of murine models in recapitulating human primary immunodeficiencies associated with PCP.
• To elucidate the role of Interleukin-21 Receptor (IL-21R) and STAT3 signaling in CD4+ T cell-mediated immunity against Pneumocystis.

Main Methods:

• Tested human genetic immunodeficiencies in mouse models to assess susceptibility to Pneumocystis infection.
• Investigated the requirement of IL-21R and STAT3 signaling in CD4+ T cells for protective immune responses.
• Administered recombinant IL-22 to Il21r-/- mice and assessed its effect on antimicrobial peptide expression.

Main Results:

• Murine models successfully recapitulated susceptibility observed in human genetic immunodeficiencies linked to PCP.
• IL-21R and STAT3 signaling within CD4+ T cells are essential for antifungal antibody and effector T cell responses.
• IL-21R/STAT3 signaling supports CD4+ T cell effector functions, including IL-22 production, which induces fungicidal cathelicidin.

Conclusions:

• SPF laboratory mice serve as valuable tools for studying human primary immunodeficiencies and CD4+ T cell immunity.
• IL-21R and STAT3 signaling pathways are critical for effective CD4+ T cell-mediated defense against Pneumocystis.